As would be expected, operators of commercial aircraft and their suppliers conduct an unending search for ways to reduce the operating costs of their aircraft. One point of focus in this search is cabin pressurization and environmental control systems (ECS). In current practice, propulsion engine bleed air from the turbine engines of such aircraft is employed for both ventilation and pressurization, the bleed air being utilized as fresh air to replace some portion of the air being circulated in a cabin. The use of bleed air from the engine may be the single largest operating cost factor in providing necessary secondary power and environmental control functions for the aircraft.
Moreover, as turbine engine technology improves, the bypass ratio of the engines is being increased and air flow in the engine core reduced, further reducing the availability of bleed air for pressurization and ventilation. Consequently, it is desirable to avoid, to the extent possible, the use of bleed air in aircraft ECS's. The present invention is directed to achieving that goal.